Nitrocellulose lacquers



May 3, 1960 COOK ETAL 2,935,414

NITROCELLULOSE LACQUERS Filed May 22, 1958 SOLVENT TO NITROCELLl/LOSE RATIO uvmvroxs. RALPH L. COOK y EUGENE A. ANDREW .QM, w h

A TTOR/Vf YS-f quer, preferably by decanting. This invention 'is predicated on the discovery that the compatibility of water in a United States Pat in: O T

. q v Ice Patented May 3, 1960' system containing water, nitrocellulose, and a water i'm-z miscible nitrocellulose solvent, is a function of the con- 293- 414 centration of the nitrocellulose in the system. Thus,

. when a relatively dilute nitrocellulose lacquer 1s prepared NITROCELLULOSE LACQUERS 5 from water wet nitrocellulose, the resultant lacquer is a homogeneous one-phase system in which the water is unif g g g {Leg- 3 g l gzd gg: forrnly incorporated. However, when the concentrz ttionv pomtionEast Alton, a corporation of Virginia or themtrocellulose 1n the lacquer is increased, water s I precipitated therefrom in amounts relatively proportional pp n M a' 737,934 to the concentration of the lacquer.

5 Claims. i 106 183) The invention is most specifically concerned with-.the preparation of lacquers from nitrocellulose containing ber tween about and 40% water. In other words, the water-to-nitrocellulose ratio of the lacquer isbetween;- This invention relat sto n tro ellul s l q s 15 about 0.25 and about 0.66. Since the water removalis. parti la y to 8 lnethod ot'minimiling the Water Content generally proportional to the concentration'of the nitrothereof. g cellulose in the lacquer, best results are obtained when the In the manufacture of globular P P Powder y lacquer is highly concentrated. Theoretically, optimum the solidification of nitrocellulose. droplets while susult ld b b i d h l a di f 1- pended ill a non-solvent medium as described i 29 vent was used to dissolve the nitrocellulose. In actual 2,740,704 and 2,740,705 granted Ap i 9 to Jo practice, however, when the ratio of the solvent-to-nitroand Gilbert Rt the lacquer is u y cellulose in the lacquer is reduced to about 1.5 :1, a very P p from fibrous nitrocellulose containing between heavy dough-like lacquer is obtained from which a major about 2 and 40% .Watef- This lacquer is most nportion of the water is precipitated. More concentrated veniently made fro'm water wet, nitrocellulose because lacquers are di l heavy d difli lt .to w k, t nitrocellulose is commercially available only in that Therefore, it is preferredknot to utilize heavierlacquers form; 3 f vgovefnn'lellit Specifications q i that inaccordance with this invention. However,,with special fibrous nitioeeliniose in Shipment contain at least equipment, it is possible to obtain a lacquer in which the water as asafety measure. Such water wet nitrocellulose ratio of h l i ll i i the i h can be readily dissolved in water immiscible nitrocellulose h d of b t 1:1, Thus, the present invention encom. Solvents to Provide a homogeneous q from this 3 passes the utilization of lacquers having this composition. suitable propellent Powder can be P p y complete Theoretically, the solvent content could be further'reduced dissolution processes. l but actually incomplete solvation of the nitrocellulose is 'If the water is not removed'from the nitrocellulose-or b bl b i d h h unt of solvent in the from the lacquer prepared therefrom, .the resultant globul q i l h h i ll l e, a

i Powder has an ohieetionabiy low gi'eviinetl'io P The nitrocellulose lacquer utilized in accordance with g density because excessive P y- Thus, in P this invention must be substantially immiscible with water.= tice, water is removed from the suspended lacquerpa While some mutual solubility of the water and solvent ticlesby adding a solute tothe non-solvent suspe can be tolerated, it must be sufficiently small sothat the,v medium as taught by Schaefer in 2,160,626. This process 40 Water and lacquer are bl of forming a two-phase Snooessfniiy remove Water from the Suspended nitroceiiu' system. It is preferred to use ethyl acetate as the solvent lose lacquer ParticleS before they are hardened ihtogiob" in the process of this invention but other water immiscible ular grains but the time of dewatering when using wa nitrocellulose solvents such as methyl 'ethyl ketoneto wet nitrocellulose is quite lengthy,-particularly when large which toluene has been added and i p l acetate can diameter grains being P This Problem also be employed. The nitrocellulose solvent must also comes particularly important in the manufacture of grains more volatile than water t facilitate the. removal of having 'a diameter in the neighborhood of 0.1' inch Or the solvent in the manufacture of globular powder grains v greaterin addition e water content of come!" since the subsequent hardening operation is carried out cially fibrous nitrocellulosewariesbetween about 20% and in an aqueous suspending medium 40%; the time for a s. also such i The solvation of the nitrocellulose and the subsequent tion necessitates periodic sampling and 'militates against removal f the Water th from can b i d t t any a uniform operational Procedure-L temperature at which water and the solvent are in the It is, therefore, an object of this invention to provide liquid state" The solubility f Water i a n l t a novel method for the removal of water from nitrocellumay vary with the nomsolvent system; however even lose lacquers Prepared [from 'f wet nitrofeuuloseasystem wheresolubility increases with temperature, it Another object of this y m .5 o Prepare mtmcenu' is preferred. to separate at a temperature slightly below lose iaequeisheving a q m, t 90 from. Water the boiling point of the particular solvent being used. in' Wet nitrocellulose Contaming i' ln degrees f order'that a minimum of this solvent be employed to give A more specific object of this invention is to provide a a workable V method 9t Preparing Water immisclbianitmcellulose In practice, the advantages of this invention are most it a lll advantageous 9? em manufacture readily achieved by adding nitrocellulose to a water imof'globular propellant powder by the processesiofiu's' miscible nitrocellulose solvent and continuing the addi-. Patents 2740704 98 57 9 h d th b tion and solution of the nitrocellulose until a lacquer z gggi g gi fig gg t g g g g gg having a solvent-to-nitrocellulose ratio of. about 1.S :l is lacquer from nitrocellulose wet with more than about obtamed- This results In t formatwn I a lacquer 20% water in a water immiscible nitrocellulose lacquer Phase a water phase Whlch can be readilyrstiparated and reducing the solventto-nitrocellulose ratio until water by any suitable means- After the Water Phase h P? is separated or precipitated from the lacquer as a separate removed, the e y q 15 then diluted y the i n phase. The water phase is then separated from the laeof solvent until a lacquer of the desired concentration is obtained. a v

The invention will be more readily understood from the following preferred embodiment taken in connection with the accompanying drawing which is a graphic presentation of the compatibility of water-ethyl acetate-nitrocellulose lacquers. All proportions throughout the specification and in this embodiment are given in parts by weight.

In the drawing, the solvent-to-nitrocellulose ratio has been plotted against the water-to-nitrocellulose ratio. The solvent-tonitrocellulose ratio shows the concentration of the nitrocellulose in the lacquer, while the water-to-nitrocellulose ratio gives the water content of the nitrocellulose used in making up the lacquer. Lacquers having compositions within area III of the graph are single phase homogeneous systems which will retain their water content, while lacquers having compositions within area II of the graph are water saturated and begin to precipitate Water therefrom. However, when the lacquers are concentrated sufiiciently for their compositions to fall within area I of the graph, water separates from them as a separate phase and can be very readily removed.

As a specific example, about 100 pounds of fibrous nitrocellulose wet With about 50 pounds of Water were mixed with about 150 pounds of ethyl acetate at a temperature of about 65 C. The water-to-nitrocellulose ratio was then 0.5 :1 and the ethyl acetate-to-nitrocellulose ratio was about :1. The composition of the mixture is plotted as point 1 on the graph. Point 1 is in area I and thus the resultant lacquer will not tolerate all of the water contained in the nitrocellulose. From the graph, it is evident that a lacquer having a solvent-to-nitrocellulose ratio of 1.5:1 will hold only 0.3 parts of water for each part of nitrocellulose. Thus, pounds of water were expelled as a separate phase and the resultant lacquer is represented as point 2 on the graph.

After the water phase was separated from this lacquer, the lacquer was diluted with an additional 150 pounds of ethyl acetate to give a lacquer having an ethyl acetateto-nitrocellulose ratio of 3:1 and a water-to-nitrocellulose ratio of only 03:1. The composition of this lacquer is shown at point 3 on the graph. It will be noted that this lacquer contains only 30 pounds of water. By contrast, if this same lacquer were prepared from the same components by adding the nitrocellulose to the ethyl acetate until a lacquer having an ethyl acetate-to-nitrocellulose ratio of about 3:1 was obtained, all of the Water originally associated with the nitrocellulose would be contained in the lacquer. The composition of a lacquer prepared by this method is designated as point 4 on the graph. It will be noted that this latter lacquer contains /2 part of Water for each part of nitrocellulose, or 20 pounds more water than does the lacquer indicated at point 3 on the graph. Thus, by the simple expedient o increasing the solventto-nitrocellulose ratio to about 1.5 :1 and then diluting, 40% of the water originally associated with the water Wet nitrocellulose has been eliminated from the system.

Globular propellent powder having an average diameter of about 0.100 inch was prepared by subdividing the lacquer of point 3 in an aqueous medium, permitting it to round up, and removing the solvent therefrom, generally in accordance with the processes of US. Patents 2,740,704 and 2,704,705. The aqueous medium consisted essentially of water having about 4% sodium sulfate dissolved therein in order to remove Water from the suspended lacquer particles generally in accordance with the teachings of US. Patent 2,160,626. In like manner, a duplicate powder was prepared from the lacquer of point 4. It was found that it was necessary to treat the lacquer of point 4 with a 4% sodium sulfate solution in accordance with the teachings of US. Patent 2,160,626 for a period of about 18 hours to obtain a powder having a packing or gravimetric density of about 950 grams per cc., whereas the lacquer of point 3 required a treatment of only 12 hours to obtain a dense powder having substantially the same gravimetric density. Thus, in accordance with the process of this invention, the dewatering time for nitrocellulose powder having a diameter of about 0.100 inch was reduced by about 33%.

In the above embodiment, ethyl acetate was used as the nitrocellulose solvent. It will be readily appreciated, however, that other water immiscible nitrocellulose solvents can be utilized with equal facility in carrying out the process of the present invention. Also, the preferred embodiment illustrated methods of reducing the solvent-tonitrocellulose ratio by the addition of nitrocellulose to the lacquer. This ratio can, of course, also be reduced by removal of solvent from the lacquer. While the dewatered lacquer of the present invention has particular utility in the manufacture of propellent powders by processes involving complete solvation of the nitrocellulose, it will be readily appreciated that this water removal process can also be used in the preparation of nitrocellulose lacquers for any other purpose.

Since variations in the specific embodiment may be made within the spirit and scope of this invention, the above description is not to be considered as limitative except in the light of the appended claims.

What is claimed is:

l. A method of preparing a nitrocellulose lacquer which comprises adding water wet fibrous nitrocellulose to an agitated water immiscible solvent until the solvent-tonitrocellulose weight ratio is about 1.5 :1 to effect the separation and Stratification of a continuous water phase, and decanting the continuous Water phase from the lacquer.

2. A method of preparing a nitrocellulose lacquer from fibrous nitrocellulose wet with more than about 0.2 parts of water for each part of nitrocellulose comprising, adding the nitrocellulose to an agitated water immiscible solvent until the solvent-to-nitrocellulose weight ratio is about 1:1 to effect the separation and Stratification of a continuous water phase, and decanting the water phase from the lacquer.

3. The method of claim 2 in which the solvent is ethyl acetate.

4. A method of making nitrocellulose lacquer having a solvent-to-nitrocellulose weight ratio greater than about 1.5 :1, which comprises adding fibrous nitrocellulose Wet with more than about 0.3 parts water for each part of nitrocellulose to an agitated water immiscible solvent until the solvent-to-nitrocellulose weight ratio is about 1.5 :1 to elfect the separation and-Stratification of a continuous Water phase, decanting the water phase from the lacquer, and diluting the lacquer.

5. The process of claim 4 in which the water immiscible solvent is ethyl acetate.

References Cited in the file of this patent UNITED STATES PATENTS 2,102,697 Gloor Dec. 21, 1937 2,114,491 Hollabaugh Apr.'19, 1938 2,292,469 Olsen Aug. 11, 1942 2,715,574 Cox Aug. 16, 1955 2,849,440 Steinmann Aug. 26, 1958 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2935, 114 May 3, 1960 Ralph L. Cook et a1.

It is herebfi certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column .5 line 61 for "2,704,705" read 2,740,705

Signed and sealed this 11th day of October 1960.

'(SEAL) Attest:

KARL H. AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,935,414 May 3, 1960 Ralph L. Cook et a1.

It is hereby certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 61, for "2,704,705" read 2,740,705

Signed and sealed this 11th day of October 1960.

(SEAL) Attest:

KARL H, AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents 

1. A METHOD OF PREPARING A NITROCELLULOSE LACQUER WHICH COMPRISES ADDING WATER WET FIBROUS NITROCELLULOSE TO AN AGITATED WATER IMMISCIBLE SOLVENT UNTIL THE SOLVENT-TONITROCELLULOSE WEIGHT RATIO IS ABOUT 1.5:1 TO EFFECT THE SEPARATION AND STRAFICATION OF A CONTINUOUS WATER PHASE, AND DECANTING THE CONTINUOUS WATER PHASE FROM THE LACQUER. 